Try some formula like this:
(array formula, ending with Ctrl+Shift+Enter)
=SUM(IF((MOD(ROW($A$1:$A$999),3)=0),$A$1:$A$999))


--
Best regards,
---
Yongjun CHEN
=================================
XLDataSoft - Data Analysis Expert, Excel/VBA Specialist
- - - - www.XLDataSoft.com - - - -
Free Excel-Based Data Processing Tool is Available for Download
Free Excel / VBA Training Materials is Available for Download
=================================
"bthieson" wrote in
message ...

I have quite a large excel sheet with about 210 columns. I need a sum at
the end of each row for every third cell. I have tried a couple
different formulas that should work, but they always end up adding
other values in for some reason. The cells I need added go like so:
E3,H3......HA3. I'm sure a few of you out there have dealt with this
before. If you have a resolution, I would definately appreciate your
response.


--
bthieson
------------------------------------------------------------------------
bthieson's Profile:
http://www.excelforum.com/member.php...o&userid=34357
View this thread: http://www.excelforum.com/showthread...hreadid=541295